diff options
Diffstat (limited to 'drivers/lguest/core.c')
| -rw-r--r-- | drivers/lguest/core.c | 369 |
1 files changed, 369 insertions, 0 deletions
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c new file mode 100644 index 000000000..312ffd3d0 --- /dev/null +++ b/drivers/lguest/core.c @@ -0,0 +1,369 @@ +/*P:400 + * This contains run_guest() which actually calls into the Host<->Guest + * Switcher and analyzes the return, such as determining if the Guest wants the + * Host to do something. This file also contains useful helper routines. +:*/ +#include <linux/module.h> +#include <linux/stringify.h> +#include <linux/stddef.h> +#include <linux/io.h> +#include <linux/mm.h> +#include <linux/vmalloc.h> +#include <linux/cpu.h> +#include <linux/freezer.h> +#include <linux/highmem.h> +#include <linux/slab.h> +#include <asm/paravirt.h> +#include <asm/pgtable.h> +#include <asm/uaccess.h> +#include <asm/poll.h> +#include <asm/asm-offsets.h> +#include "lg.h" + +unsigned long switcher_addr; +struct page **lg_switcher_pages; +static struct vm_struct *switcher_vma; + +/* This One Big lock protects all inter-guest data structures. */ +DEFINE_MUTEX(lguest_lock); + +/*H:010 + * We need to set up the Switcher at a high virtual address. Remember the + * Switcher is a few hundred bytes of assembler code which actually changes the + * CPU to run the Guest, and then changes back to the Host when a trap or + * interrupt happens. + * + * The Switcher code must be at the same virtual address in the Guest as the + * Host since it will be running as the switchover occurs. + * + * Trying to map memory at a particular address is an unusual thing to do, so + * it's not a simple one-liner. + */ +static __init int map_switcher(void) +{ + int i, err; + + /* + * Map the Switcher in to high memory. + * + * It turns out that if we choose the address 0xFFC00000 (4MB under the + * top virtual address), it makes setting up the page tables really + * easy. + */ + + /* We assume Switcher text fits into a single page. */ + if (end_switcher_text - start_switcher_text > PAGE_SIZE) { + printk(KERN_ERR "lguest: switcher text too large (%zu)\n", + end_switcher_text - start_switcher_text); + return -EINVAL; + } + + /* + * We allocate an array of struct page pointers. map_vm_area() wants + * this, rather than just an array of pages. + */ + lg_switcher_pages = kmalloc(sizeof(lg_switcher_pages[0]) + * TOTAL_SWITCHER_PAGES, + GFP_KERNEL); + if (!lg_switcher_pages) { + err = -ENOMEM; + goto out; + } + + /* + * Now we actually allocate the pages. The Guest will see these pages, + * so we make sure they're zeroed. + */ + for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) { + lg_switcher_pages[i] = alloc_page(GFP_KERNEL|__GFP_ZERO); + if (!lg_switcher_pages[i]) { + err = -ENOMEM; + goto free_some_pages; + } + } + + /* + * We place the Switcher underneath the fixmap area, which is the + * highest virtual address we can get. This is important, since we + * tell the Guest it can't access this memory, so we want its ceiling + * as high as possible. + */ + switcher_addr = FIXADDR_START - (TOTAL_SWITCHER_PAGES+1)*PAGE_SIZE; + + /* + * Now we reserve the "virtual memory area" we want. We might + * not get it in theory, but in practice it's worked so far. + * The end address needs +1 because __get_vm_area allocates an + * extra guard page, so we need space for that. + */ + switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE, + VM_ALLOC, switcher_addr, switcher_addr + + (TOTAL_SWITCHER_PAGES+1) * PAGE_SIZE); + if (!switcher_vma) { + err = -ENOMEM; + printk("lguest: could not map switcher pages high\n"); + goto free_pages; + } + + /* + * This code actually sets up the pages we've allocated to appear at + * switcher_addr. map_vm_area() takes the vma we allocated above, the + * kind of pages we're mapping (kernel pages), and a pointer to our + * array of struct pages. + */ + err = map_vm_area(switcher_vma, PAGE_KERNEL_EXEC, lg_switcher_pages); + if (err) { + printk("lguest: map_vm_area failed: %i\n", err); + goto free_vma; + } + + /* + * Now the Switcher is mapped at the right address, we can't fail! + * Copy in the compiled-in Switcher code (from x86/switcher_32.S). + */ + memcpy(switcher_vma->addr, start_switcher_text, + end_switcher_text - start_switcher_text); + + printk(KERN_INFO "lguest: mapped switcher at %p\n", + switcher_vma->addr); + /* And we succeeded... */ + return 0; + +free_vma: + vunmap(switcher_vma->addr); +free_pages: + i = TOTAL_SWITCHER_PAGES; +free_some_pages: + for (--i; i >= 0; i--) + __free_pages(lg_switcher_pages[i], 0); + kfree(lg_switcher_pages); +out: + return err; +} +/*:*/ + +/* Cleaning up the mapping when the module is unloaded is almost... too easy. */ +static void unmap_switcher(void) +{ + unsigned int i; + + /* vunmap() undoes *both* map_vm_area() and __get_vm_area(). */ + vunmap(switcher_vma->addr); + /* Now we just need to free the pages we copied the switcher into */ + for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) + __free_pages(lg_switcher_pages[i], 0); + kfree(lg_switcher_pages); +} + +/*H:032 + * Dealing With Guest Memory. + * + * Before we go too much further into the Host, we need to grok the routines + * we use to deal with Guest memory. + * + * When the Guest gives us (what it thinks is) a physical address, we can use + * the normal copy_from_user() & copy_to_user() on the corresponding place in + * the memory region allocated by the Launcher. + * + * But we can't trust the Guest: it might be trying to access the Launcher + * code. We have to check that the range is below the pfn_limit the Launcher + * gave us. We have to make sure that addr + len doesn't give us a false + * positive by overflowing, too. + */ +bool lguest_address_ok(const struct lguest *lg, + unsigned long addr, unsigned long len) +{ + return addr+len <= lg->pfn_limit * PAGE_SIZE && (addr+len >= addr); +} + +/* + * This routine copies memory from the Guest. Here we can see how useful the + * kill_lguest() routine we met in the Launcher can be: we return a random + * value (all zeroes) instead of needing to return an error. + */ +void __lgread(struct lg_cpu *cpu, void *b, unsigned long addr, unsigned bytes) +{ + if (!lguest_address_ok(cpu->lg, addr, bytes) + || copy_from_user(b, cpu->lg->mem_base + addr, bytes) != 0) { + /* copy_from_user should do this, but as we rely on it... */ + memset(b, 0, bytes); + kill_guest(cpu, "bad read address %#lx len %u", addr, bytes); + } +} + +/* This is the write (copy into Guest) version. */ +void __lgwrite(struct lg_cpu *cpu, unsigned long addr, const void *b, + unsigned bytes) +{ + if (!lguest_address_ok(cpu->lg, addr, bytes) + || copy_to_user(cpu->lg->mem_base + addr, b, bytes) != 0) + kill_guest(cpu, "bad write address %#lx len %u", addr, bytes); +} +/*:*/ + +/*H:030 + * Let's jump straight to the the main loop which runs the Guest. + * Remember, this is called by the Launcher reading /dev/lguest, and we keep + * going around and around until something interesting happens. + */ +int run_guest(struct lg_cpu *cpu, unsigned long __user *user) +{ + /* If the launcher asked for a register with LHREQ_GETREG */ + if (cpu->reg_read) { + if (put_user(*cpu->reg_read, user)) + return -EFAULT; + cpu->reg_read = NULL; + return sizeof(*cpu->reg_read); + } + + /* We stop running once the Guest is dead. */ + while (!cpu->lg->dead) { + unsigned int irq; + bool more; + + /* First we run any hypercalls the Guest wants done. */ + if (cpu->hcall) + do_hypercalls(cpu); + + /* Do we have to tell the Launcher about a trap? */ + if (cpu->pending.trap) { + if (copy_to_user(user, &cpu->pending, + sizeof(cpu->pending))) + return -EFAULT; + return sizeof(cpu->pending); + } + + /* + * All long-lived kernel loops need to check with this horrible + * thing called the freezer. If the Host is trying to suspend, + * it stops us. + */ + try_to_freeze(); + + /* Check for signals */ + if (signal_pending(current)) + return -ERESTARTSYS; + + /* + * Check if there are any interrupts which can be delivered now: + * if so, this sets up the hander to be executed when we next + * run the Guest. + */ + irq = interrupt_pending(cpu, &more); + if (irq < LGUEST_IRQS) + try_deliver_interrupt(cpu, irq, more); + + /* + * Just make absolutely sure the Guest is still alive. One of + * those hypercalls could have been fatal, for example. + */ + if (cpu->lg->dead) + break; + + /* + * If the Guest asked to be stopped, we sleep. The Guest's + * clock timer will wake us. + */ + if (cpu->halted) { + set_current_state(TASK_INTERRUPTIBLE); + /* + * Just before we sleep, make sure no interrupt snuck in + * which we should be doing. + */ + if (interrupt_pending(cpu, &more) < LGUEST_IRQS) + set_current_state(TASK_RUNNING); + else + schedule(); + continue; + } + + /* + * OK, now we're ready to jump into the Guest. First we put up + * the "Do Not Disturb" sign: + */ + local_irq_disable(); + + /* Actually run the Guest until something happens. */ + lguest_arch_run_guest(cpu); + + /* Now we're ready to be interrupted or moved to other CPUs */ + local_irq_enable(); + + /* Now we deal with whatever happened to the Guest. */ + lguest_arch_handle_trap(cpu); + } + + /* Special case: Guest is 'dead' but wants a reboot. */ + if (cpu->lg->dead == ERR_PTR(-ERESTART)) + return -ERESTART; + + /* The Guest is dead => "No such file or directory" */ + return -ENOENT; +} + +/*H:000 + * Welcome to the Host! + * + * By this point your brain has been tickled by the Guest code and numbed by + * the Launcher code; prepare for it to be stretched by the Host code. This is + * the heart. Let's begin at the initialization routine for the Host's lg + * module. + */ +static int __init init(void) +{ + int err; + + /* Lguest can't run under Xen, VMI or itself. It does Tricky Stuff. */ + if (get_kernel_rpl() != 0) { + printk("lguest is afraid of being a guest\n"); + return -EPERM; + } + + /* First we put the Switcher up in very high virtual memory. */ + err = map_switcher(); + if (err) + goto out; + + /* We might need to reserve an interrupt vector. */ + err = init_interrupts(); + if (err) + goto unmap; + + /* /dev/lguest needs to be registered. */ + err = lguest_device_init(); + if (err) + goto free_interrupts; + + /* Finally we do some architecture-specific setup. */ + lguest_arch_host_init(); + + /* All good! */ + return 0; + +free_interrupts: + free_interrupts(); +unmap: + unmap_switcher(); +out: + return err; +} + +/* Cleaning up is just the same code, backwards. With a little French. */ +static void __exit fini(void) +{ + lguest_device_remove(); + free_interrupts(); + unmap_switcher(); + + lguest_arch_host_fini(); +} +/*:*/ + +/* + * The Host side of lguest can be a module. This is a nice way for people to + * play with it. + */ +module_init(init); +module_exit(fini); +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>"); |